1 //===---- llvm/Analysis/ScalarEvolutionExpander.h - SCEV Exprs --*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the classes used to generate code from scalar expressions.
12 //===----------------------------------------------------------------------===//
14 #ifndef LLVM_ANALYSIS_SCALAREVOLUTION_EXPANDER_H
15 #define LLVM_ANALYSIS_SCALAREVOLUTION_EXPANDER_H
17 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
18 #include "llvm/Analysis/ScalarEvolutionNormalization.h"
19 #include "llvm/Support/IRBuilder.h"
20 #include "llvm/Support/TargetFolder.h"
21 #include "llvm/Support/ValueHandle.h"
27 /// SCEVExpander - This class uses information about analyze scalars to
28 /// rewrite expressions in canonical form.
30 /// Clients should create an instance of this class when rewriting is needed,
31 /// and destroy it when finished to allow the release of the associated
33 class SCEVExpander : public SCEVVisitor<SCEVExpander, Value*> {
36 // New instructions receive a name to identifies them with the current pass.
39 std::map<std::pair<const SCEV *, Instruction *>, AssertingVH<Value> >
41 std::set<AssertingVH<Value> > InsertedValues;
42 std::set<AssertingVH<Value> > InsertedPostIncValues;
44 /// RelevantLoops - A memoization of the "relevant" loop for a given SCEV.
45 DenseMap<const SCEV *, const Loop *> RelevantLoops;
47 /// PostIncLoops - Addrecs referring to any of the given loops are expanded
48 /// in post-inc mode. For example, expanding {1,+,1}<L> in post-inc mode
49 /// returns the add instruction that adds one to the phi for {0,+,1}<L>,
50 /// as opposed to a new phi starting at 1. This is only supported in
51 /// non-canonical mode.
52 PostIncLoopSet PostIncLoops;
54 /// IVIncInsertPos - When this is non-null, addrecs expanded in the
55 /// loop it indicates should be inserted with increments at
57 const Loop *IVIncInsertLoop;
59 /// IVIncInsertPos - When expanding addrecs in the IVIncInsertLoop loop,
60 /// insert the IV increment at this position.
61 Instruction *IVIncInsertPos;
63 /// Phis that complete an IV chain. Reuse
64 std::set<AssertingVH<PHINode> > ChainedPhis;
66 /// CanonicalMode - When true, expressions are expanded in "canonical"
67 /// form. In particular, addrecs are expanded as arithmetic based on
68 /// a canonical induction variable. When false, expression are expanded
69 /// in a more literal form.
72 /// When invoked from LSR, the expander is in "strength reduction" mode. The
73 /// only difference is that phi's are only reused if they are already in
77 typedef IRBuilder<true, TargetFolder> BuilderType;
81 const char *DebugType;
84 friend struct SCEVVisitor<SCEVExpander, Value*>;
87 /// SCEVExpander - Construct a SCEVExpander in "canonical" mode.
88 explicit SCEVExpander(ScalarEvolution &se, const char *name)
89 : SE(se), IVName(name), IVIncInsertLoop(0), IVIncInsertPos(0),
90 CanonicalMode(true), LSRMode(false),
91 Builder(se.getContext(), TargetFolder(se.TD)) {
98 void setDebugType(const char* s) { DebugType = s; }
101 /// clear - Erase the contents of the InsertedExpressions map so that users
102 /// trying to expand the same expression into multiple BasicBlocks or
103 /// different places within the same BasicBlock can do so.
105 InsertedExpressions.clear();
106 InsertedValues.clear();
107 InsertedPostIncValues.clear();
111 /// getOrInsertCanonicalInductionVariable - This method returns the
112 /// canonical induction variable of the specified type for the specified
113 /// loop (inserting one if there is none). A canonical induction variable
114 /// starts at zero and steps by one on each iteration.
115 PHINode *getOrInsertCanonicalInductionVariable(const Loop *L, Type *Ty);
117 /// hoistStep - Utility for hoisting an IV increment.
118 static bool hoistStep(Instruction *IncV, Instruction *InsertPos,
119 const DominatorTree *DT);
121 /// replaceCongruentIVs - replace congruent phis with their most canonical
122 /// representative. Return the number of phis eliminated.
123 unsigned replaceCongruentIVs(Loop *L, const DominatorTree *DT,
124 SmallVectorImpl<WeakVH> &DeadInsts,
125 const TargetLowering *TLI = NULL);
127 /// expandCodeFor - Insert code to directly compute the specified SCEV
128 /// expression into the program. The inserted code is inserted into the
130 Value *expandCodeFor(const SCEV *SH, Type *Ty, Instruction *I);
132 /// setIVIncInsertPos - Set the current IV increment loop and position.
133 void setIVIncInsertPos(const Loop *L, Instruction *Pos) {
134 assert(!CanonicalMode &&
135 "IV increment positions are not supported in CanonicalMode");
137 IVIncInsertPos = Pos;
140 /// setPostInc - Enable post-inc expansion for addrecs referring to the
141 /// given loops. Post-inc expansion is only supported in non-canonical
143 void setPostInc(const PostIncLoopSet &L) {
144 assert(!CanonicalMode &&
145 "Post-inc expansion is not supported in CanonicalMode");
149 /// clearPostInc - Disable all post-inc expansion.
150 void clearPostInc() {
151 PostIncLoops.clear();
153 // When we change the post-inc loop set, cached expansions may no
155 InsertedPostIncValues.clear();
158 /// disableCanonicalMode - Disable the behavior of expanding expressions in
159 /// canonical form rather than in a more literal form. Non-canonical mode
160 /// is useful for late optimization passes.
161 void disableCanonicalMode() { CanonicalMode = false; }
163 void enableLSRMode() { LSRMode = true; }
165 /// clearInsertPoint - Clear the current insertion point. This is useful
166 /// if the instruction that had been serving as the insertion point may
167 /// have been deleted.
168 void clearInsertPoint() {
169 Builder.ClearInsertionPoint();
172 void setChainedPhi(PHINode *PN) { ChainedPhis.insert(PN); }
175 LLVMContext &getContext() const { return SE.getContext(); }
177 /// InsertBinop - Insert the specified binary operator, doing a small amount
178 /// of work to avoid inserting an obviously redundant operation.
179 Value *InsertBinop(Instruction::BinaryOps Opcode, Value *LHS, Value *RHS);
181 /// ReuseOrCreateCast - Arange for there to be a cast of V to Ty at IP,
182 /// reusing an existing cast if a suitable one exists, moving an existing
183 /// cast if a suitable one exists but isn't in the right place, or
184 /// or creating a new one.
185 Value *ReuseOrCreateCast(Value *V, Type *Ty,
186 Instruction::CastOps Op,
187 BasicBlock::iterator IP);
189 /// InsertNoopCastOfTo - Insert a cast of V to the specified type,
190 /// which must be possible with a noop cast, doing what we can to
192 Value *InsertNoopCastOfTo(Value *V, Type *Ty);
194 /// expandAddToGEP - Expand a SCEVAddExpr with a pointer type into a GEP
195 /// instead of using ptrtoint+arithmetic+inttoptr.
196 Value *expandAddToGEP(const SCEV *const *op_begin,
197 const SCEV *const *op_end,
198 PointerType *PTy, Type *Ty, Value *V);
200 Value *expand(const SCEV *S);
202 /// expandCodeFor - Insert code to directly compute the specified SCEV
203 /// expression into the program. The inserted code is inserted into the
204 /// SCEVExpander's current insertion point. If a type is specified, the
205 /// result will be expanded to have that type, with a cast if necessary.
206 Value *expandCodeFor(const SCEV *SH, Type *Ty = 0);
208 /// isInsertedInstruction - Return true if the specified instruction was
209 /// inserted by the code rewriter. If so, the client should not modify the
211 bool isInsertedInstruction(Instruction *I) const {
212 return InsertedValues.count(I) || InsertedPostIncValues.count(I);
215 /// getRelevantLoop - Determine the most "relevant" loop for the given SCEV.
216 const Loop *getRelevantLoop(const SCEV *);
218 Value *visitConstant(const SCEVConstant *S) {
219 return S->getValue();
222 Value *visitTruncateExpr(const SCEVTruncateExpr *S);
224 Value *visitZeroExtendExpr(const SCEVZeroExtendExpr *S);
226 Value *visitSignExtendExpr(const SCEVSignExtendExpr *S);
228 Value *visitAddExpr(const SCEVAddExpr *S);
230 Value *visitMulExpr(const SCEVMulExpr *S);
232 Value *visitUDivExpr(const SCEVUDivExpr *S);
234 Value *visitAddRecExpr(const SCEVAddRecExpr *S);
236 Value *visitSMaxExpr(const SCEVSMaxExpr *S);
238 Value *visitUMaxExpr(const SCEVUMaxExpr *S);
240 Value *visitUnknown(const SCEVUnknown *S) {
241 return S->getValue();
244 void rememberInstruction(Value *I);
246 void restoreInsertPoint(BasicBlock *BB, BasicBlock::iterator I);
248 bool isNormalAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
250 bool isExpandedAddRecExprPHI(PHINode *PN, Instruction *IncV, const Loop *L);
252 Value *expandAddRecExprLiterally(const SCEVAddRecExpr *);
253 PHINode *getAddRecExprPHILiterally(const SCEVAddRecExpr *Normalized,
257 Value *expandIVInc(PHINode *PN, Value *StepV, const Loop *L,
258 Type *ExpandTy, Type *IntTy, bool useSubtract);